Fix sample variables
This fixes #15 (closed).
The first patch has already been sent to the mailing-list, but dropping it prevents the latter patch from having any effect. So here you go, both of them in one go. If the first one hits upstream as-is, rebasing should work fine.
This needs https://gitlab.freedesktop.org/kusma/mesa/commits/virgl-set_min_samples also. I'll submit that one for the corresponding mesa-branch once this has landed.